IC card

ABSTRACT

An IC card capable of reinforcing the prevention of the electrostatic damage without causing a rise in the cost of a semiconductor integrated circuit chip. The semiconductor integrated circuit chip ( 2 ) is mounted on a card substrate ( 1 ), and plural connection terminals ( 3 ) are exposed. The connection terminals are connected to predetermined external terminals ( 4 ) of the semiconductor integrated circuit chip, first overvoltage protection elements ( 7, 8, 9 ) connected to the external terminals are integrated in the semiconductor integrated circuit chip, and second overvoltage protection elements such as surface-mount type varistors ( 11 ) connected to the connection terminals are mounted on the card substrate. The varistors are variable resistor elements having a current tolerating ability greater than that of the first overvoltage protection elements. The varistors have been selected by taking into consideration a relationship between the characteristics and the ability of the first overvoltage protection elements contained in the semiconductor integrated circuit chip, and exhibit the effect for preventing the electrostatic damage.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of application Ser. No. 10/408,256filed Apr. 8, 2003, now U.S. Pat. No. 7,224,052, which is a division ofapplication Ser. No. 09/689,663 filed Oct. 13, 2000 (now U.S. Pat. No.6,573,567 issued Jun. 3, 2003).

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to technology for suppressing ESD (alsocalled electrostatic discharge damage) of a semiconductor integratedcircuit chip mounted on an IC card. More particularly, the inventionrelates to technology that can be effectively adapted to memory cardssuch as multi-media cards.

2. Prior Art

A variety of memory cards have heretofore been provided for storingmulti-media data in compact sizes having decreased weights. For example,there has been provided a multi-media card having a memory and a memorycontroller mounted on a card substrate, establishing an interface to ahost unit using a small number of signals.

Giving priority to a small size and reduced weight, the memory card ofthis type has the connection terminals for connection to the host unit,the connection terminals being exposed on the card substrate, but has noparticular mechanism such as cover for protecting the terminals. Whenthe exposed terminals are touched at the time when the memory card isremoved from the host unit, therefore, a semiconductor integratedcircuit chip connected to the exposed terminals may be damaged. Usually,the semiconductor integrated circuit chip is provided with an inputprotection circuit for preventing the input circuit from theelectrostatic damage. The input protection circuit is constituted by,for example, disposing, between an input terminal and a power sourceterminal, an element such as a diode whose connection state is reversedrelative to the amplitude voltage of the input signal. It is, however,expected that the memory card is carried by itself and is frequentlyattached to, and detached from, the host unit. Thus, the presentinventors have found the importance of reinforcing the prevention of theelectrostatic damage.

Though the technical field is different from the above memory card,Japanese Patent Laid-Open No. 209379/1998 discloses technology forreinforcing the protection of input against the electrostatic damage.According to this technology, a metal wiring layer is formed maintaininga gap (discharge gap) in which static electricity could be dischargedrelative to an electrode layer on a semiconductor substrate so that whenstatic electricity has entered into the electrode layer, the staticelectricity is discharged to the metal wiring layer, preventing thestatic electricity that has entered into the electrode layer fromentering into the semiconductor element. Further, Japanese PatentLaid-Open No. 271937/1995 discloses a circuit employing a gate-sourceprotection diode of a MOSFET that is externally attached to asemiconductor integrated circuit chip to prevent the electrostaticdamage.

There has further been provided a varistor of semiconductor ceramicsfrom the standpoint of protecting the circuitry from an overvoltage.

SUMMARY OF THE INVENTION

The present inventors have forwarded the following study from thestandpoint reinforcing the prevention of electrostatic damage of the ICcard such as a memory card having connection terminals that are exposed.

First, it became obvious that when Zener diodes of a large size areintegrated on a semiconductor integrated circuit chip to obtain anenergy withstand amount that helps reinforce the prevention ofelectrostatic damage, the area efficiency decreases in the midst of finecircuit elements, driving up the cost to a conspicuous degree.

Second, when an element for protection from an overvoltage is attachedto the semiconductor integrated circuit chip to reinforce the preventionof electrostatic damage, the efficiency for preventing the electrostaticdamage does not increase unless consideration is given to a relationshipbetween the characteristics and the ability of the overvoltageprotection circuit incorporated in the semiconductor integrated circuitchip. Besides, the externally attached circuit elements that are largein size or that are large in number, cause an increase in the size andthickness of the IC card. Such a viewpoint has not been taught by theabove prior art. In this specification, the overvoltage stands for asurge voltage or a transient voltage that generates electrostatically.

Third, even when the countermeasure against the electrostatic damage istaken by using the externally attached circuit elements, there is noguarantee that the device is absolutely safe from the damage when it ishandled in an unexpected manner by a person who is not familiar with. Itis therefore necessary to make perfection more perfect.

Fourth, even when the input circuit of the semiconductor integratedcircuit is electrostatically damaged, it can be expected that the datain the memory remain safe. In such a case, recovering the data from thememory card gives an excellent feature relieving the data and offeringan increased safety of the memory card as a storage medium.

Fifth, a countermeasure against the electrostatic damage by theexternally attached circuit elements, decreases, at least, the vacantregion on the card substrate correspondingly. Even in this case, itbecomes necessary to avoid concentration of wiring patterns and theconcentration of bonding wires that could become a cause of malfunctiondue to undesired leakage of signal lines. This contrivance is necessaryeven when the memory capacity of the memory card is to be increased.

The present invention provides an IC card capable of reinforcing theprevention of electrostatic damage without driving up the cost of thesemiconductor integrated circuit chip.

The present invention further provides an IC card capable of reinforcingthe prevention of electrostatic damage by attaching overvoltageprotection elements to the semiconductor integrated circuit chip withoutcausing a great change in the size and thickness of the card.

The invention further provides an IC card which can be expected toprevent electrostatic damage caused by an unexpected handling by aperson who is not familiar with.

The invention further provides an IC card capable of easily recoveringthe data in the memory card even when the input circuit of thesemiconductor integrated circuit chip is electrostatically damaged,provided the data in the memory remain safe.

The invention further provides an IC card capable of avoiding theconcentration of wiring patterns and bonding wires that could cause amalfunction due to undesired leakage of signal lines even when thevacant region on the card substrate is decreased by the countermeasureagainst the electrostatic damage by externally attaching the circuitelements.

The invention further provides an IC card having a relatively largestorage capacity in a relatively small size.

The above and other objects as well as novel features of the presentinvention will become obvious from the description of the specificationand the accompanying drawings.

Briefly described below are representative examples of the inventiondisclosed in this application.

[1] Second overvoltage protection elements capable of reinforcing theprevention of electrostatic damage are externally attached to thesemiconductor integrated circuit chip by taking into consideration arelationship to first overvoltage protection elements that areintegrated in a semiconductor integrated circuit chip. That is, an ICcard has a semiconductor integrated circuit chip mounted on a cardsubstrate and plural connection terminals that are exposed, wherein theconnection terminals are connected to predetermined external terminalsof the semiconductor integrated circuit chip, the first overvoltageprotection elements connected to the external terminals are integratedon the semiconductor integrated circuit chip, and the second overvoltageprotection elements connected to the connection terminal are mounted onthe card substrate.

According to a first aspect, the second overvoltage protection elementsare variable resistor elements having a current tolerating abilitygreater than that of the first overvoltage protection elements.

According to a second aspect, a voltage greater than a rated voltageapplied to the second overvoltage protection elements for flowing aspecified pulse current, is the voltage that enables the firstovervoltage protection elements to flow only a current smaller than theabove specifued pulse current.

According to a third aspect, the second overvoltage protection elementsare variable resistor elements having a breakdown voltage larger thanthat of the first overvoltage protection elements.

According to a fourth aspect, the second overvoltage protection elementshave a capacity larger than that of the first overvoltage protectionelements.

This enables a high-speed surge pulse to be by-passed through a lowresistance.

According to a fifth aspect, the second overvoltage protection elementshave a breakdown voltage smaller than a breakdown voltage of the firstovervoltage protection elements.

According to a sixth aspect, the second overvoltage protection elementshas a breakdown voltage smaller than a breakdown voltage of a circuitthat is protected by the first overvoltage protection elements.

In any aspect, it can be said that the second overvoltage protectionelements exhibit the effect for preventing the electrostatic damage,since consideration has been given to a relationship between thecharacteristics and the ability of the first overvoltage protectionelements that are contained in the semiconductor integrated circuitchip.

The second overvoltage protection elements may have their ends on oneside thereof connected to the power source connection terminals of thecard substrate and may have their ends on the other side thereofconnected to the signal connection terminals. The signal connectionterminals are connected to the corresponding external terminals of thesemiconductor integrated circuit chip. Here, the signal propagationdistances from the signal connection terminals to the correspondingsecond overvoltage protection elements are shorter than the signalpropagation distances from the signal connection terminals to thecorresponding external terminals of the semiconductor integrated circuitchip. This prevents the semiconductor integrated circuit chip from beingdirectly affected destructively by the overvoltage before the secondovervoltage protection elements work in response to the overvoltage.

The second overvoltage protection elements may be varistors of thesurface-mount type comprising chiefly semiconductor ceramics, an arrayof chip diodes, chip capacitors or chip transistors. This makes itpossible to decrease the mounting area or the occupation area of thesecond overvoltage protection elements. The surface mounting lowers thecost of production.

When a memory card such as a multi-media card is used as an IC card, thesemiconductor chip is a controller chip, and one or plural memory chips(e.g., nonvolatile memory chips) connected to the controller chip arefurther mounted on the card substrate. The controller chip has a memorycontrol function for controlling the reading/writing operation for thememory chips according to an instruction from an external unit.

When a consideration is given to data security and copyright, thecontroller chip may employ a privacy protection function for effectingthe encryption for the data written into the memory chip and foreffecting the decryption for the data read out from the memory chip.

When a consideration is given to preventing the electrostatic damageeven during the steps of manufacturing the IC card, the secondovervoltage protection elements connected to the connection terminalsshould be mounted on the card substrate, first, and, then, predeterminedexternal terminals of the semiconductor integrated circuit chip shouldbe connected to the connection terminals. Then, the protection by thesecond overvoltage protection elements is obtained in a step ofconnecting the semiconductor integrated circuit chip.

[2] The invention is concerned with an IC card having a semiconductorintegrated circuit chip mounted on a card substrate, wherein pluralconnection terminals are exposed, predetermined external terminals ofsaid semiconductor integrated circuit chip are connected to theconnection terminals, first overvoltage protection elements connected tothe external terminals are integrated on the semiconductor integratedcircuit chip, and second overvoltage protection elements connected tothe connection terminals are mounted on the card substrate, and whereinthe second overvoltage protection elements may be connected by beingsurface-mounted on the electrically conducting pattern formed on thecard substrate. This makes it possible to decrease the cost of mountingthe second overvoltage protection elements.

When a memory card such as a multi-media card is used as the IC card,the semiconductor chip is a controller chip, and one or plural memorychips connected to the controller chip are further mounted on the cardsubstrate. Here, bonding wires are used for connecting the connectionterminals to the external terminals of the controller chip, and bondingwires are used for connecting the controller chip to the memory chips.Therefore, a number of wiring patterns having the same function as theconnection by the bonding wires, need not be densely formed on the cardsubstrate. Space on the controller chip or the memory chips can be usedfor the wiring. Accordingly, this contributes to decreasing the cost ofthe card substrate.

When plural memory chips are to be connected in parallel to thecontroller chip by bonding wires, the memory chips may be mounted on thecard substrate in a manner that the chips are stacked one upon the otherwith their positions being so deviated that the external terminals areexposed, from the standpoint of shortening the lengths of the bondingwires. Therefore, the distance to the controller chip is shortened andthe lengths of the bonding wires are shortened compared to when thememory chips are arranged without being stacked one upon the other. Thisdecreases the probability of undesired contact or breakage of thebonding wires. In this case, in particular, a condition should bemaintained in that the area on one surface of the card substrate islarger than the total areas of the memory chips and of the controllerchip. This is to provide the card substrate with extra space forsufficiently coping with a restrictive condition in that the wiringlayer is formed on one surface only of the card substrate. This is not asimple idea of mounting the memory chips in a stacked manner fordecreasing the area of the card substrate.

[3] The invention is concerned with an IC card in which plural memorychips and the controller chip for controlling the memory chips aremounted on one surface of the card substrate, wherein when the memorychips are mounted on the card substrate in a manner of being stacked oneupon the other with their positions being so deviated that the externalterminals are exposed, the external terminals of the memory chips thatreceive the same signals from the controller chip are successivelyconnected in series by bonding the wires. The bonding method of aso-called stitch sewing is employed. The bonding wires can be shortenedas a whole compared to when the controller chip is connected to theexternal terminals through the bonding wires. In this respect, too, theprobability of undesired contact or breakage of lines due to theconcentration of the bonding wires can be decreased.

The invention is concerned with an IC card in which plural memory chipsand the controller chip for controlling the memory chips are mounted onone surface of the card substrate, wherein when the memory chips aremounted on the card substrate in a manner of being stacked one upon theother with their positions being so deviated that the external terminalsare exposed, the external terminals for receiving chip selection signalsof the memory chips are located at the ends of the arrangements of theexternal terminals of the nonvolatile memory chips, and are connected tothe controller chip by bonding the wires. In a constitution forseparately selecting the plural memory chips, the external terminals forreceiving the chip selection signals must be separately connected to theexternal terminals for outputting the chip selection signal of thecontroller chip. Therefore, the above stitch-bonding method cannot beemployed. However, the external terminals for selecting the chips arearranged at the ends of the memory chips and work to accomplishnecessary connection without hindered by other bonding wires.

[4] The memory chips and the controller chip mounted on the cardsubstrate may be arranged in the form of columns. That is, the memorychips are connected to the controller chip, the connection terminalsformed on the card substrate are connected to predetermined externalterminals of the controller chip, the first overvoltage protectionelements connected to the external terminals are integrated on thecontroller chip, and the second overvoltage protection elementsconnected to the connection terminals are mounted on the card substrate.The distances from the connection terminals are increased in order ofthe second overvoltage protection elements, controller chip, and pluralmemory chips, which are arranged like columns from one side of the cardsubstrate to the opposing side thereof. Owing to this column-likearrangement, the second overvoltage protection elements for finallyreleasing the overvoltage are located closest to the connectionterminals to which an overvoltage is applied, and the memory chipsstoring the data are located remotest, offering a high reliability fromthe standpoint of preventing electrostatic damage to the semiconductorchip and protecting the data.

In this case, too, the memory chips may be mounted on the card substratein a manner of being stacked one upon the other with their positionsbeing so deviated that the external terminals are exposed.

The arrangement of the memory chips and the controller chip mounted onthe card substrate is not limited to the column-like arrangement only.When plural connection terminals are arranged along one side between thetwo neighboring sides of the card substrate, the memory controller isarranged with its lengthwise direction in parallel with the other sideof the two neighboring sides, and plural memory chips are arranged inparallel in a direction nearly at right angles with the direction inwhich the connection terminals are arranged. The connection terminalsexposed from the card substrate are connected to predetermined externalterminals of the controller chip, the first overvoltage protectionelements connected to the external terminals are integrated on thecontroller chip, and the memory chips are connected to the controllerchip. With the connection terminals and the controller chip beingarranged along the neighboring two sides of the card substrate, it isallowed to easily increase the density for mounting the memory chips orto increase the number of mounts. If the memory chips are arranged inparallel being divided into a first group in which the memory chips arestacked in a plural number with their positions being so deviated thatthe external terminals are exposed and a second group in which thememory chips are stacked in a plural number in the same manner, theheight of the IC card can be suppressed. The second overvoltageprotection elements connected to the connection terminals may be mountedon the card substrate along the direction in which the connectionterminals are arranged.

[5] When an IC card is constituted by forming electrically conductingpatterns on both surfaces of the card substrate, the electricallyconducting patterns may be connected by using through holes that arepenetrating through the card substrate. In this case, it is desired thatthe through holes are arranged outside the molded region that covers thesemiconductor integrated circuit chip and the other surface of the cardsubstrate. The molding that is executed while applying a pressureeliminates the probability in that the molding resin flows into the backside of the card substrate passing through the holes.

When the through holes are formed for the connection terminals exposedfrom the IC card, it is desired that the through holes are formed atpositions deviated from the slide surfaces of the connection terminals.Even when the IC card is attached to, or detached from, the mountingslot, therefore, the terminals of the slot do not come into slidecontact with the through holes and do not receive mechanical force,preventing such a probability that the patterns of the connectionterminals are cracked from the through holes and are damaged.

The invention is concerned with an IC card in which plural connectionterminals are exposed on one surface of a card substrate, asemiconductor integrated circuit chip is mounted on the other surface ofthe card substrate, predetermined external terminals of thesemiconductor integrated circuit chip are connected to the connectionterminals, first overvoltage protection elements connected to theexternal terminals are integrated on the semiconductor integratedcircuit chip, and second overvoltage protection elements connected tothe connection terminals are mounted on the other surface of the cardsubstrate, and wherein the semiconductor integrated circuit chip, thesecond overvoltage protection elements and the other surface of the cardsubstrate are covered with a metal cap. The metal cap can be formed byreducing a metal plate, by a forging method or by a die casting method.This provides a countermeasure against EMI (electromagneticinterference) compared to the resin cap, and helps accomplish thesealing by mechanical fastening and accomplish the cap-sealing at a hightemperature. The resin cap may be blended with an electromagneticwave-absorbing material such as ferrite, etc. To cope with ESD,electrically conducting particles such as carbon may be mixed.

An electrically conducting shielding pattern may be employed for thecard substrate to relax the effect of electrostatic discharge that takesplace near the card substrate. That is, the invention is concerned withan IC card in which plural connection terminals are exposed on onesurface of a card substrate, and a semiconductor integrated circuit chipis mounted on the other surface of the card substrate, whereinpredetermined external terminals of the semiconductor integrated circuitchip are connected to the connection terminals, first overvoltageprotection elements connected to the external terminals are integratedon the semiconductor integrated circuit chip, second overvoltageprotection elements connected to the connection terminals are mounted onthe other surface of the card substrate, and an electrically conductingshielding pattern is formed on one surface of the card substrate excepta region of the connection terminals, the electrically conductingshielding pattern being connected to the connection terminal forsupplying ground power source or being connected to none of theconnection terminals. The electrically conducting shielding patterndisperses the static electricity.

[6] From the standpoint of preventing electrostatic damage of when theIC card is handled in an unexpected manner by a person who is notfamiliar with, the IC card is provided on the surface thereof with anindication indicating a position where the IC card should be held byfingers (figure of a finger printed on a position at where the IC cardshould be held by fingers at the time of attachment or detachment), theIC card mounting a semiconductor integrated circuit chip permittingplural connection terminals to be exposed. Further, a notice is writtenon the surface of the IC card warning not to touch the connectionterminals. Besides, a notice is written on the packing member packingthe IC card warning not to touch the connection terminals of the ICcard.[7] The invention deals with a IC card giving attention to recoveringthe stored data, wherein plural connection terminals are exposed, pluralmemory chips and a controller chip for controlling the memory chips aremounted on a card substrate, the connection terminals are connected to afirst group of external terminals of the controller chip, the memorychips are connected to a second group of external terminals of thecontroller chip, and data evaluation terminals connected to the secondgroup of external terminals are formed on the card substrate.

In case the controller chip becomes no longer capable of executing thememory control due to electrostatic damage, access can be made directlyto the memory chips from an external unit through the data evaluationterminals. Therefore, even when the controller chip is destroyed, thedata remaining in the memory chips can be easily recovered.

The card substrate may further be provided with a control terminal forcontrolling the output terminal included in the second group of externalterminals of the controller chip to assume a high output impedancestate. The damaged controller chip that is placed in an undesired signaloutput state, can be easily relieved.

The controller chip may often be provided with a privacy protectionmechanism for executing the encryption for the data that are writteninto the memory chips and for executing the decryption for the data readout from the memory chips. In this case, the data are recovered by themanufacturer of the IC card or by an authorized person by decrypting thedata read out from the memory chips.

[8] The simplest method of recovering the data from the IC card havingthe data evaluation terminals, includes a first processing for placingthe memory chips in a state where they cannot be controlled by thecontroller chip, and a second processing for reading out the data fromthe data evaluation terminals by controlling the memory chips. A datarecovery method of when the controller chip has the privacy protectionfunction, includes a first processing for controlling the outputterminal included in the second group of external terminals of thecontroller chip to assume a high output impedance state, a secondprocessing for reading out the data from the data evaluation terminalsby controlling the memories, a third processing for decrypting the dataread out by the second processing, and a fourth processing for writingthe data decrypted by the third processing into another IC card.

Therefore, even in case the input circuit of the semiconductorintegrated circuit chip is electrostatically damaged, the data thatremain safe in the memory can be easily recovered.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a circuit diagram illustrating a connection terminal of an ICcard according to the present invention;

FIG. 2 is an axial sectional view illustrating the structure of avaristor in cross section;

FIG. 3 is a diagram of an I-V line illustrating the characteristics ofthe varistor;

FIG. 4 is a diagram illustrating the connection of the varistors to theconnection terminals of a multi-media card;

FIG. 5 is a diagram illustrating, on a plane, the constitution of themulti-media card chiefly in a state where the circuit elements aremounted;

FIG. 6 is a vertical sectional view of the multi-media card of FIG. 5;

FIG. 7 is a diagram illustrating a state where a through hole is formedin a deviated manner in a connection terminal of the multi-media card;

FIG. 8 is a plan view partly illustrating the multi-media card byapplying stitch bonding for connecting the nonvolatile memory chips;

FIG. 9 is a vertical sectional view of a stitch-bonded portion;

FIG. 10 is a diagram illustrating the wire bondings of when a nail headbonding is utilized and when a wedge bonding is utilized;

FIG. 11 is a diagram illustrating, on a plane, the constitution of amulti-media card having a structure in which four pieces of nonvolatilememory chips are stacked;

FIG. 12 is a vertical sectional view illustrating the sectionalstructure of the multi-media card of FIG. 11;

FIG. 13 is a plan view illustrating a multi-media card applying astructure for stacking the memory chips in a divided manner and astructure in which the connection terminals and the controller chip arearranged along the two neighboring sides of the card substrate;

FIG. 14 is a vertical sectional view illustrating a portion of themulti-media card of FIG. 13;

FIG. 15 is a plan view illustrating another multi-media card applying astructure for stacking the memory chips in a divided manner and astructure in which the connection terminals and the controller chip arearranged along the two neighboring sides of the card substrate;

FIG. 16 is a plan view illustrating a memory card in which thecontroller chip is placed on the memory chip to stack both of them;

FIG. 17 is a plan view illustrating a folded card by stacking the memorychips and the controller chip by utilizing LOC;

FIG. 18 is a plan view illustrating another IC card applying a COBstructure;

FIG. 19 is a vertical sectional view of the IC card of FIG. 18;

FIG. 20 is a view illustrating an electrically conducting pattern formedon the bottom surface of a card substrate of the IC card of FIG. 18;

FIG. 21 is a view illustrating an IC card describing a notice or a signof caution for preventing electrostatic damage;

FIG. 22 is a flowchart illustrating a method of fabricating an IC cardmounting varistors;

FIG. 23 is a plan view of an IC card giving attention to recovering thedata;

FIG. 24 is a flowchart illustrating a procedure of a data recoveryprocessing for an IC card having data evaluation terminals;

FIG. 25 is a diagram illustrating several kinds of structures of metalcaps;

FIG. 26 is a block diagram illustrating the constitution of a flushmemory chip; and

FIG. 27 is a sectional view schematically illustrating the structure ofa nonvolatile memory cell transistor for the flush memory chip.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

<Reinforcing the Function for Preventing Electrostatic Damage by UsingVaristors>

First, described below is a principle for reinforcing the function forpreventing electrostatic damage to the semiconductor integrated circuitby using externally attached circuit elements such as varistors.

FIG. 1 illustrates a connection terminal of an IC card according to theinvention. The IC card that is shown has a semiconductor integratedcircuit chip 2 mounted on a card substrate 1, and, typically, hasconnection terminals 3 that are exposed. The connection terminals 3 areinterface terminals for electrically connecting the IC card to a hostunit to which the IC card is detachably attached.

The connection terminals 3 are connected to predetermined externalterminals 4 of the semiconductor integrated circuit chip 2. The externalterminals are input terminals which are connected to, for example, aCMOS inverter in the initial stage of the input circuit via signal lines5. The CMOS inverter is constituted by a p-channel field-effecttransistor (often described as unit MOS transistor) Q1 and an n-channelMOS transistor Q2 disposed in series between a ground terminal Vss and apower source terminal Vcc of the circuit. In the semiconductorintegrated circuit chip 2 are integrated diodes 7, 8 which are firstovervoltage protection elements connected to the external terminal 4, athyristor 9 and a clamping MOS transistor Q5. On the card substrate 1 ismounted a varistor 11 which is a second overvoltage protection elementconnected to the connection terminal 3. The diodes 7, 8, thyristor 9 andclamping MOS transistor Q5 constitute an input protection circuit 6.

The concept of cathode and drain of the MOS transistor is determineddepending upon the direction of the operation voltage. In thisspecification, for convenience, the names determined in the state ofnormal operation by the operation voltages Vss and Vcc are used as thenames of terminals.

The anode of the diode 7 is connected to the input signal line 4, thecathode thereof is connected to the power source terminal Vcc, thecathode of another diode 8 is connected to the input signal line 4 andthe anode thereof is connected to the ground terminal Vss. The thyristor9 is equivalently constituted by a pnp transistor Q3 and an npntransistor Q4, and the anode thereof is connected to the input signalline 4, and the cathode thereof is connected to the ground terminal Vss.The MOS transistor Q5 is a clamping MOS transistor of the form of aso-called diode connection of which the gate and source are connected tothe ground terminal Vss and of which the drain is connected to the inputsignal line 4.

Reference numerals 12 and 13 are input protection resistors. Symbols Q6and Q7 are a p-channel clamping MOS transistor of the form of aso-called diode connection of which the gate and source are connectedtogether and an n-channel clamping MOS transistor. The clamping MOStransistors Q6 and Q7 are circuit elements having an auxiliary functionto cope with the case where an overvoltage has leaked from the inputprotection circuit 6. When used alone, they cannot work as the firstovervoltage protection element but work as the overvoltage protectionelement in cooperation with other circuit element.

In a normal state, the connection terminal 3 receives a signal having avoltage amplitude between the ground voltage Vss and the power sourcevoltage Vcc. In this case, the diodes 7, 8, thyristor 9, and clampingMOS transistors Q5, Q6 and Q7 are all connected in a reversed manner.

When an overvoltage of a positive polarity is applied to the connectionterminal 3 due to electrostatic discharge, the diode 7 is connected inthe forward direction, the anode of the thyristor 9 is turned on inexcess of the element voltage in the forward direction, whereby theovervoltage flows into the power source voltage Vcc and the groundvoltage Vss, and is blocked from flowing into the succeeding stages orflows in a decreased amount. The clamping MOS transistor Q6 is turned onwhen the overvoltage of the positive polarity leaks even by a smallamount, and permits the overvoltage to flow into the power sourcevoltage Vcc.

On the other hand, when an overvoltage of a negative polarity is appliedto the connection terminal 3 due to electrostatic discharge, the diode 8is connected in the forward direction and the clamping MOS transistor Q5is turned on, whereby the overvoltage flows into the ground voltage Vss,and is blocked from flowing into the succeeding stages or flows in adecreased amount. The clamping MOS transistor Q7 is turned on when theovervoltage of the negative polarity leaks even by a small amount, andpermits the overvoltage to flow into the ground voltage Vss.

The varistor 11 is a circuit element which assumes the overvoltageelement operation before the overvoltage element operation of the inputprotection circuit 6 reaches its limit, and reinforces the function forpreventing electrostatic damage or reinforces the overvoltage protectionfunction. The varistor 11 is equivalent to a circuit in which the Zenerdiodes are connected back to back, or can be replaced thereby.

Here, the varistor 11 is a laminated chip varistor using semiconductorceramics. Referring to an axial sectional view of FIG. 2, the varistor11 has the shape of a small chip that can be surface-mounted, haselectrically conducting side electrodes 20 and 21 at both ends, the oneside electrode 20 being provided with a pair of interlayer electrodes 22and 23 extending toward the other side electrode 21, the other sideelectrode 21 being provided with another interlayer electrode 24 locatedbetween the pair of interlayer electrodes 22 and 23, and extendingtoward the one side electrode 20, and the gaps among the side electrodes20, 21 and the interlayer electrodes 22, 23, 24 being filled withsemiconductor ceramics 25.

FIG. 3 illustrates characteristics of the varistor 11. The varistor 11is a variable resistor element having current-voltage (I-V)characteristics as shown in FIG. 3, operates on a leakage current of notlarger than 50 μA in a state where it is normally used, and does notaffect the input of signals through the connection terminal 3 in a statewhere the device is practically used. This state is obtained by usingthe device at a voltage which is not higher than a rated voltage (alsocalled use voltage) Vwm specific to the varistor as described in a datasheet thereof. When an abnormally high voltage enters into thesemiconductor integrated circuit chip, the input protection circuit inthe semiconductor integrated circuit chip starts working at a relativelylow voltage. However, the current tolerating ability of the overvoltageprotection element such as diode in the input protection circuit becomesno longer sufficient for the overvoltage, and the current saturates.Accordingly, the operation current starts flowing into the varistor 11.Then, as the overvoltage reaches near the breakdown voltage (Vb), theresistance so decreases that the voltage becomes almost constantirrespective of the current. For larger transient voltage, the varistorprevents the electrostatic damage to the semiconductor integratedcircuit chip owing to its high energy allowance value with the clampvoltage (Vc) as a theoretical upper limit.

Let it now be presumed a case where a voltage of 10 kilovolts which isfar greater than an electrostatic breakdown voltage of several hundredvolts to 2 kilovolts of the semiconductor integrated circuit chip, isapplied at a current of 1000 A for 10 nanoseconds (10 nS) to the IC cardto which a varistor 11 having an energy withstand level of 0.2 J (Joule)is attached. In this case, the amount of energy is 10 kV×1000 A×10 nS0.1 J. This amount of energy is smaller than the above energy withstandlevel of the varistor 11, and the electrostatic damage is prevented.

In FIG. 3, the clamp voltage Vc can be specified to be a prescriptivepulse current, i.e., as a terminal voltage (voltage across the sideelectrodes) of when a current of 1 A is supplied for 8.20 seconds, andthe breakdown voltage Vb can be specified to be a terminal voltage ofwhen, for example, a current of 1 mA is supplied. If describedqualitatively, the breakdown voltage Vb can be defined as a voltagewhich easily enables the I-V characteristics to be reversed even when adirect current is applied within the range. The clamp voltage can bedefined to be a voltage that is very likely to lead to the breakage whenit is exceeded several times.

The characteristics of the varistor 11 can be specified to be asdescribed below by taking into consideration the characteristics of theovervoltage protection element of the input protection circuit 6.

First, the varistor 11 can be specified to be a variable resistanceelement having an current tolerating ability in excess of that of thediodes 7, 8, thyristor 9 and clamping MOS transistor Q5 in the inputprotection circuit 6, or in excess of that of the clamping MOStransistors Q6 and Q7.

Second, a voltage such as a breakdown voltage Vb or a voltage closethereto larger than a rated voltage applied to the varistor 11 forflowing a specified pulse current, is the voltage that enables thediodes 7, 8, thyristor 9, clamping MOS transistor Q5 in the inputprotection circuit 6, and the clamping MOS transistors Q6 and Q7 to flowonly a current smaller than the above specified pulse current, if theyare not broken.

Third, the varistor 11 is a variable resistance element having abreakdown voltage larger than those of the diodes 7, 8, thyristor 9 andclamping MOS transistor Q5 in the input protection circuit 6, and thanthose of the clamping MOS transistors Q6 and Q7.

Fourth, the varistor 11 is a variable resistance element having a straycapacity larger than those of the diodes 7, 8, thyristor 9 and clampingMOS transistor Q5 in the input protection circuit 6, and than those ofthe clamping MOS transistors Q6 and Q7. As will be understood from thestructure of FIG. 2, when used for the power source terminal, it isobvious that the semiconductor ceramics has a relatively largecapacitive component though it is not a dielectric. Thus, the straycapacity works to relax the change in the transient voltage, and iseffective for preventing the electrostatic damage when the straycapacity is large. When used for signal terminals, the capacity must bedecreased to lie within a permissible range so as to respond tohigh-speed signals.

Fifth, the breakdown voltage of the varistor 11 is smaller than thebreakdown voltages of the diodes 7, 8, thyristor 9 and clamping MOStransistor Q5 in the input protection circuit 6, and than those of theclamping MOS transistors Q6 and Q7. The varistor 11 breaks down beforethe input protection circuit 6 is damaged to let the overvoltage bereleased.

Sixth, the breakdown voltage of the varistor 11 is smaller than thebreakdown voltages of the diodes 7, 8, thyristor 9 and clamping MOStransistor Q5 in the input protection circuit 6, and than that of acircuit protected by the clamping MOS transistors Q6 and Q7, such as ofa CMOS inverter circuit constituted by MOS transistors Q1 and Q2.

As described above, the varistor 11 has been selected by taking intoconsideration the relationship between the characteristics and theability of the overvoltage protection elements such as diodes 7, 8constituting the input protection circuit 6 contained in thesemiconductor integrated circuit chip 2. Accordingly, the varistor 11efficiently exhibits the effect for preventing the electrostatic damage.

The signal propagation distance from the connection terminal 3 to thevaristor 11 is shorter than the signal propagation distance of from theconnection terminal 3 to a corresponding external terminal 4 of thesemiconductor integrated circuit chip 2. This makes it possible toprevent the semiconductor integrated circuit chip 2 from directlyreceiving destructive effect due to an overvoltage before the varistor11 functions in response to the overvoltage.

The varistor 11 is of the source-mounting type comprising chieflysemiconductor ceramics. Therefore, the mounting area or the occupationarea of the varistor 11 can be decreased. The surface mounting helpsdecrease the cost of producing the IC card.

<Application to a Multi-Media Card>

Described below is an embodiment in which the IC card using the varistor11 is applied to a multi-media card.

FIG. 4 is a diagram illustrating the connection of the varistors to theconnection terminals of the multi-media card. According to thespecifications by the Group of Standardization, the multi-media card hasa size measuring 24 mm×32 mm×1.4 mm. The card substrate 1 has connectionterminals, i.e., a connection terminal 3 a for receiving a chip selectsignal CS, a connection terminal 3 b for receiving a command CMD, aconnection terminal 3 c for receiving a clock signal CLK, a connectionterminal 3 d for inputting and outputting data DAT, a connectionterminal 3 e served with a power source voltage Vcc, and two connectionterminals 3 f and 3 g served with ground voltage Vss. The connectionterminals 3 a to 3 g are connected to the controller chip and to thenonvolatile memory chips that are not shown but that are mounted on aregion designated at 30 in the drawing. In FIG. 4, the arrangement ofthe connection terminals 3 a to 3 g is different from that of thepractical multi-media card.

Varistors 11 a to 11 e are mounted on the card substrate 1 among theconnection terminals 3 a to 3 e and between the connection terminals 3 eand 3 g. In FIG. 4, the varistor is provided in a number of one for eachcorresponding terminal. The varistors, however, may be provided in aplural number being connected in series.

In particular, the varistor 11 e disposed for the connection terminal 3e that receives the power source voltage Vcc, works as a by-passcapacitor. Therefore, the varistor 11 e may be replaced by a by-passcapacitor, or a by-pass capacitor 31 may be arranged in parallel asshown in FIG. 4.

FIG. 5 illustrates on a plane the constitution of the multi-media cardmounting chiefly the circuit elements, and FIG. 6 is a verticalsectional view thereof. The card substrate 1 is constituted by a glassepoxy resin, and has, on the back surface thereof, the connectionterminals 3 a to 3 g formed as electrically conducting patterns. On thesurface of the card substrate 1 are mounted the varistors 11 a to 11 e,a controller chip 33 and nonvolatile memory chips 34 a, 34 b via wiringpatterns and electrically conducting patterns. In FIG. 5, referencenumeral 36 denotes electrically conducting patterns connected to thecorresponding connection terminals 3 a to 3 g via the through holes 40,and reference numeral 35 denotes a wiring pattern for connecting theends of the varistors 11 a to 11 e to the ground voltage Vss. Thevaristors 11 a to 11 e are surface-mounted spanning across the wiringpattern 35 and the connection terminals 3 a to 3 e.

In FIG. 5, reference numerals 38 and 39 denote bonding patterns, and 37denotes wiring patterns connecting the bonding patterns 38 to theelectrically conducting patterns 36. The electrically conductingpatterns 38 are connected to the corresponding external terminals 50 ofthe controller chip 33 through bonding wires 41, and the externalterminals 51 of the controller chip 33 are connected to thecorresponding bonding patterns 39 through bonding wires 42. The bondingpatterns 39 are connected to the corresponding external terminals 52 aof one nonvolatile memory chip 34 a by bonding wires 43 a, and thebonding patterns 39 are connected to the corresponding externalterminals 52 b of the other nonvolatile memory chip 34 b by bondingwires 43 b. The semiconductor integrated circuit chip is a so-calledbear chip, and the external terminals 50, 51, 52 a and 52 b are thebonding pads formed of aluminum, aluminum alloy, copper or the like.

The nonvolatile memory chips 34 a and 34 b are, for example,electrically rewritable flush memory chips. The flush memory chip has amemory cell array in which are arranged, like a matrix, nonvolatilememory cell transistors having a control gate, a floating gate, a sourceand a drain, and executes such operations as reading the data, erasingthe data, writing the data and verifying the data according to commandsand addresses fed from an external unit. The nonvolatile memory chips 34a and 34 b comprising the flush memory chips have external terminals 52a and 52 b, which are terminals for receiving a chip enable signal (alsocalled chip selection signal) /CE for instructing the selection of chip,terminals for receiving a write enable signal /WE for instructing thewriting operation, input/output terminals I/O0 to I/O7, terminals forreceiving a command/data enable signal /CDE for instructing whether theinput/output terminals I/O0 to I/O7 be used for inputting/outputting thecommand/data or for receiving the address, terminals for receiving anoutput enable signal /OE for instructing the output operation, terminalsfor receiving a clock signal /SC for instructing the data latch timing,a terminal for outputting a ready/busy signal R/B for instructing to anexternal unit whether the writing operation is being executed, andterminals for receiving a reset signal /RES.

The controller chip 33 has a privacy protection function which controlsthe reading/writing operation for the nonvolatile memory chips 34 a, 34b according to an instruction from an external unit, executes theencryption for the data to be written into the nonvolatile memory chips34 a, 34 b by taking into consideration the data security or thecopyright protection, and executes the decryption for the data read outfrom the nonvolatile memory chips 34 a and 34 b.

The external terminals 50 of the controller chip 33 are corresponded tothe input/output functions of the connection terminals 3 a to 3 g, andinclude a terminal for receiving a select signal CS for instructing theselection operation of the multi-media card, a terminal for seriallyreceiving the command CMD for instructing the operation of themulti-media card, a terminal for receiving a clock signal CLK that isregarded to be in synchronism with the signal input/output operation ofthe external terminal 50, a terminal for serially inputting/outputtingthe data DAT, and a terminal for receiving a power source voltage Vccand ground voltage Vss. In the controller chip 33 are integrated theinput protection circuit 6 and clamping MOS transistors Q6 and Q7 thatare described with reference to FIG. 1 concerning the input terminalsthat are among the external terminals 50.

The controller chip 33 has external terminals 51 for making access tothe memories, i.e., a terminal for sending a chip selection signal /CE0to the nonvolatile memory chip 34 a, a terminal for sending a chipselection signal /CE1 to the nonvolatile memory chip 34 b, and externalterminals corresponding to the external terminals of the nonvolatilememory chips 34 a and 34 b but having an input/output direction oppositethereto.

<Connection of the Bonding Wires>

As described above, bonding wires 41 are used for connecting theconnection terminals 3 a to 3 g to the external terminals 50 of thecontroller chip 33, and bonding wires 43 a and 43 b are used forconnecting the controller chip 33 to the nonvolatile memory chips 34 a,34 b. This eliminates the need of forming a number of wiring patternshaving the same function as the connection by the above bonding wires ina concentrated manner on the card substrate 1. Space on the controllerchip 33 and on the nonvolatile memory chips 34 a, 34 b can be utilizedfor the wiring. In effect, the aerial wiring of the bonding wires makesit possible to simplify the wiring on the substrate. Therefore, thiscontributes to decreasing the cost of the card substrate 1.

<Stacked Mounting in a Deviated Manner>

In the constitution of FIG. 2, the two nonvolatile memory chips 34 a and34 b are connected using the bonding wires in parallel with thecontroller chip 33. Here, the nonvolatile memory chips 34 a and 34 b aremounted on the card substrate 1 in a state of being stacked one upon theother with their positions being so deviated that the external terminals52 a, 52 b are exposed. Therefore, the distances to the controller chip33 can be shortened compared to when the nonvolatile memory chips 34 a,34 b are arranged without being stacked, and the lengths of the bondingwires 43 a, 43 b can be shortened. This decreases undesired contact orbreakage of the bonding wires. When plural nonvolatile memory chips arestacked, the amount of deviation may be determined within such a rangethat a chip of the lower layer exits under the external terminals forbonding of the chip of the upper layer. When the chip of the lower layeris not existing under the external terminals for bonding, the chip islikely to be damaged due to mechanical force at the time of bonding.

At this moment, in particular, a condition is satisfied in that the areaon one surface of the card substrate 1 is larger than the total areas ofthe nonvolatile memory chips 34 a, 34 b and the controller chip 33. Thisis a contrivance for providing the card substrate 1 with an extra spaceto cope with such a restrictive condition that the wiring layer isformed on one surface only of the card substrate. This is different froma simple idea of mounting the nonvolatile memory chips in a stackedmanner to decrease the area of the card substrate 1.

<Column-Like Layout>

In the example of FIG. 5, the nonvolatile memory chips 34 a, 34 b andthe controller chip 33 are mounted on the card substrate 1 beingarranged like columns. That is, the distance from the connectionterminals 3 a to 3 g of the multi-media card is increased in order ofthe varistors 11 a to 11 e, the controller chip 33 and the plural memorychips 34 a, 34 b, and they are arranged like columns from one side ofthe card substrate 1 toward the opposing side thereof. Owing to thiscolumn-like arrangement, the second varistors 11 a to 11 e for finallyreleasing the overvoltage are closest to the connection terminals 3 a to3 g to which the overvoltage will be applied, and the nonvolatile memorychips 34 a, 34 b storing the data are the remotest, producing the effectfor absorbing the surge of high-speed pulses. Therefore, a highreliability is obtained in regard to reinforcing the prevention ofelectrostatic damage to the controller chip 33 owing to the varistors 11a to 11 e, and to protecting the data stored in the nonvolatile memorychips 34 a and 34 b.

<Deviation of Through Holes from the Connection Terminals>

As shown in FIG. 5, the through holes 40 are formed at deviatedpositions in the connection terminals 3 a to 3 g. That is, as shown indetail in FIG. 7(A), the through hole 40 is formed in the connectionterminal 3 a exposed from the IC card at a position deviated from theslide surface of the connection terminal 3 a. The position of deviationmay be as shown in FIG. 7(B). Then, even when the IC card is attachedto, or detached from, the mounting slot, the terminal 40A of the slotdoes not come into slide contact with the through hole 40 and does notexert a mechanical force to the through hole 40. This prevents aprobability in that the pattern of the connection terminal 3 a iscracked starting from the through hole 40, or the periphery of thethrough hole is worn out causing a damage thereto.

<Formation of Through Holes Outside the Molding Region>

Referring to FIG. 6, the controller chip 33 and the nonvolatile memorychips 34 a, 34 b as a whole are molded with a thermosetting resin 55.The varistor element may be provided inside the mold or outside themold. Here, no through hole 40 is included in the region molded with thethermosetting resin 55. This precludes such a probability that themolding resin 55 flows to the back side of the card substrate 1 throughthe holes 40 to cause defective molding when the molding is effectedwith the application of pressure.

<Metal Cap>

In FIG. 6, a metal cap 56 is covering the surface of the card substrate1 on where there are mounted varistors 11 a to 11 e, controller chip 33and nonvolatile memory chips 34 a, 34 b outside the mold. This providesa countermeasure against EMI (electro magnetic interference) as comparedwith the resin cap, accomplishing the sealing by mechanical fastening orthe sealing of cap at a high temperature.

FIG. 25 illustrates several kinds of structures of the metal caps 56.FIG. 25(A) illustrates a metal cap formed by forging piece by piece inan isolated manner and having a small step for sticking a label, FIG.25(B) illustrates a metal cap formed by forging followed by blankingpiece by piece in an isolated manner, and FIG. 25(C) illustrates a metalcap formed by reducing a metal plate. FIG. 25(D) is a perspective viewof when the metal cap obtained by reducing the metal plate of FIG. 25(C)is viewed from the back side. Corner portions have been cut way inadvance to avoid wrinkles at the time of reduction.

<Stitch Bonding>

FIG. 8 illustrates a portion of the multi-media card in which thenonvolatile memory chips are connected by stitch bonding. FIG. 9 is avertical sectional view illustrating the stitch-bonded portions. Like inFIG. 5, the nonvolatile memory chips 34 a and 34 b are mounted on thecard substrate 1 in a manner of being stacked in a plural number butwith their positions being so deviated that their external terminals 52a, 52 b are exposed. Here, the external terminals 52 a, 52 b of thenonvolatile memory chips that receive the same signals from thecontroller chip 33 are successively connected in series with the bondingwires 57. Thus, there is employed a bonding method like a so-calledstitch-sewing, i.e., a stitch-bonding method. The bonding wires can beshortened as a whole compared to the case of connecting the controllerchip 33 to the external terminals 52 a, 52 b using separate bondingwires 43 a, 43 b as is done in FIG. 5. Besides, the number of thebonding wires can be decreased in the region of bonding patterns. Inthis respect, too, it is allowed to decrease the probability ofundesired contact or breakage of the contact wires that occurs when theyare arranged too densely. The nonvolatile memory chips 34 a, 34 b mustbe selected separately. The stitch-bonding cannot be employed for thebonding wires 43 a, 43 b for transmitting the chip selection signals/CE0, /CE1; i.e., the wires 43 a, 43 b are bonded in the same manner asin FIG. 5.

When the stitch-bonding is employed, the method of bonding the bondingpads 52 a may differ depending upon the form of bonding by a wire bonderthat is used. FIG. 10(A) illustrates the case of when the nail headbonding is utilized. In this case, due to the structure of the wirebonder, the end of the bonding wire is torn away like a crescent.Therefore, the next bonding point must be another place from the endpoint. Namely, the stitch bonding is completed with bonding wires 57, 57that are inevitably cut into plural pieces. FIG. 10(B), on the otherhand, illustrates a case of utilizing the wedge bonding. By using a wirebonder which supports this method, the bonding can be successivelyeffected to the subsequent positions without cutting the bonding wire.According to this system, therefore, the stitch-bonding can be effectedby using a single bonding wire 57.

FIG. 11 illustrates on a plane the constitution of the multi-media cardhaving a structure in which four pieces of nonvolatile memory chips arestacked. FIG. 12 is a vertical sectional view thereof. The four piecesof nonvolatile memory chips 34 a to 34 d are mounted on the cardsubstrate 1 being stacked with their positions being so deviated thatthe external terminals 52 a to 52 d are exposed. Here, the externalterminals 52 a to 52 d of the nonvolatile memory chips 34 a to 34 d thatreceive the same signals from the controller chip 33 are successivelyconnected in series using the bonding wires 60 like the stitch-bonding.The nonvolatile memory chips 34 a to 34 d must be separately selected.Therefore, the stitch-bonding is not employed for the bonding wires 43 ato 43 d for transmitting the chip selection signals /CE0 to /CE3; i.e.,the wires 43 a to 43 d are bonded in the same manner as in FIG. 5.However, the stitch-bonding can be effected if the chip selection signalis generated in the form of an ID command.

<Shielding Pattern>

The constitution of FIG. 11 employs an electrically conducting shieldingpattern 61 shown in FIG. 12 for the card substrate 1 in order to furtherrelax the effect of electrostatic discharge taking place near the cardsubstrate. That is, the wide electrically conducting shielding pattern61 is formed on the exposed surfaces of the connection terminals 3 a to3 g of the card substrate 1. Though there is no particular limitation,the electrically conducting shielding pattern 61 may be connected to theconnection terminals 3 f, 3 g for supplying ground power source Vss, ormay be floated since it has a relatively large surface area. Theelectrically conducting shielding pattern 61 disperses the staticelectricity.

<CS Input Terminal at an End of the Chip>

In the structure in which the plural nonvolatile memory chips 34 a to 34d are stacked being deviated as shown in FIG. 11, the terminals forreceiving the chip selection signals /CE0 to /CE3 among the externalterminals 52 a to 52 d of the nonvolatile memory chips 34 a to 34 d, arelocated at the ends of the arrangements of the external terminals, andare separately connected to the external terminals 51 of the controllerchip 33 through the bonding wires 43 a to 43 d. Quite the same holdseven for the stacked structure of FIG. 8. In the constitution in whichthe plural nonvolatile memory chips are separately selected as shown inFIGS. 8 and 11, the terminals for receiving the chip selection signalamong the external terminals of the nonvolatile memory chips must beseparately connected to the external terminals 51 for producing a chipselection signal of the controller chip 33. Even if the stitch-bondingmethod cannot be adapted to these portions, therefore, a necessaryconnection can be accomplished without hindered by other bonding wiressince the external terminals for receiving the chip selection signalhave been disposed at the ends of the nonvolatile memory chips. Theeffect appears conspicuously as the number of the nonvolatile memorychips that are stacked increases. When two pieces of nonvolatile memorychips are stacked as shown in FIG. 5, two bonding wires can be easilydrawn in parallel from a single bonding pattern by using a wire bonderhaving a high degree of precision. In this case, too, no inconvenienceoccurs even when the external terminal for receiving the chip selectionsignal is disposed at an end of the chip though the stitch-bonding isnot employed.

<Mounting the Stacked Nonvolatile Memory Chips in Plural Groups>

FIG. 13 is a view illustrating another example of the multi-media card,and FIG. 14 is a vertical sectional view illustrating a portion thereof.In the multi-media card shown in FIG. 13, two sets of nonvolatile memorychips are mounted on the card substrate 1, each set comprising twopieces of nonvolatile memory chips that are stacked, and a single-phasewiring is formed on one surface only of the card substrate 1, thesingle-phase wiring including wiring patterns and bonding patternstogether with the connection terminals. This is the so-called COB(chip-on-board) structure mounting a semiconductor bear chip on thesubstrate.

In FIG. 13, the connection terminals 3 a to 3 g, wiring patterns 35, 37,bonding pattern 38, bonding patterns 39A, 39C, and wiring pattern 39Bare all formed on the mounting side of the card substrate 1. Theconnection terminals 3 a to 3 g and the wiring pattern 35 are exposed onthe surface through openings formed in the card substrate 1, enablingthe varistors 11 a to 11 e to be connected. Similarly, the bondingpatterns 38, 39A and 39C are exposed on the surface through openingsformed in the card substrate 1, so as to be bonded to the externalterminals 50, 51 of the controller chip 33 and to the external terminals52 a to 52 d of the nonvolatile memory chips 34 a to 34 d. In FIG. 13,the stitch-bonding is employed to neither the bonding between thebonding pattern 39A and the external terminals 52 a, 52 b of thenonvolatile memory chips 34 a, 34 b nor to the bonding between thebonding pattern 39C and the external terminals 52 c, 52 d of thenonvolatile memory chips 34 c, 34 d. However, the stitch-bonding same asthat of FIG. 8 may be employed except for the chip selection signals.

When two sets of the nonvolatile memory chips are mounted on the cardsubstrate 1, each set comprising two pieces of nonvolatile memory chipsthat are stacked as shown in FIG. 13, the thickness can be decreasedcompared to when four pieces are stacked as in FIG. 11. Therefore, whentwo sets of the nonvolatile memory chips are mounted on the cardsubstrate 1, each set comprising four pieces of nonvolatile memory chipsthat are stacked, then, the storage capacity of two folds as great canbe obtained with the same height as that of the four-piece-stackedstructure of FIG. 11.

When plural connection terminals 3 a to 3 g are arranged along a side ofthe card substrate 1, the card controller 33 may be arranged with itslengthwise direction in parallel with the neighboring side and thenonvolatile memory chip may be arranged in a direction nearly at rightangles with the direction of arrangement of the connection terminals 3 ato 3 g. Then, the nonvolatile memory chips can be efficiently mounted onthe surface of the card substrate 1.

The divisional stacked structure and the structure for arranging theconnection terminals 3 a to 3 g and the controller chip 33 along the twosides of the card substrate 1, make it easy to mount the nonvolatilememory chips on the card substrate of a specified size maintaining anincreased density or to mount the nonvolatile memory chips in aincreased number.

FIG. 15 illustrates a further multi-media card employing the abovedivisional stacked structure and a structure in which the connectionterminals and the controller chip are arranged along the two neighboringsides of the card substrate. This example is different from that of FIG.13 in regard to that the connection terminals, wiring patterns andbonding patterns are formed on both surfaces of the card substrate 1 andthat the directions of the stacked nonvolatile memory chips areoriented.

In FIG. 15, the connection terminals 3 a to 3 g and the wiring patterns39B are formed on the back surface of the card substrate, and the wiringpatterns 35, 37, bonding pattern 38, and bonding patterns 39A, 39C areformed on the surface of the card substrate 1. Through holes 40A areused for connecting the wiring pattern 39B to the bonding patterns 39A,39C. Like in FIG. 13, FIG. 15 does not employ the stitch bonding,either. However, the stitch bonding like that of FIG. 8 may be employedexcept for the chip selection signals.

Like that of FIG. 13, the divisional stacked structure and the structurefor arranging the connection terminals 3 a to 3 g and the controllerchip 33 along the two sides of the card substrate 1 in the multi-mediacard of FIG. 15, make it easy to mount the nonvolatile memory chips onthe card substrate of a specified size maintaining an increased densityor to mount the nonvolatile memory chips in an increased number.

Here, the through holes in the mold may be filled with an electricallyconducting paste or a solder resist to prevent the leakage of themolding resin.

<Structure for Stacking the Memory Chips and the Controller Chip>

FIGS. 16 and 17 illustrate examples in which the controller chip ismounted and stacked on the memory chip. In FIG. 16, the externalterminals 51 of the controller chip 33 are connected to the externalterminals 52 of the nonvolatile memory chip 34 based on the directinterchip bonding by using the bonding wires 70. In order to decreasethe resistance for feeding the operation power sources Vss, Vcc to thenonvolatile memory chip 34, however, power source wiring patterns 71A,72A are formed on the back surface of the card substrate 1, and thebonding patterns 71B, 72B connected through the holes 71D, 72D areconnected to the nonvolatile memory chip 34 through the bonding wires71C, 72C. When the resistance for feeding the power to the nonvolatilememory chip 34 is very small, however, the power sources Vcc, Vss may befed through the terminals 51 and 52. The structure for mounting thevaristors 11 a to 11 e is the same as the one described above, and thecircuit elements having the same functions as those of FIG. 15 aredenoted by the same reference numerals but their description is notrepeated.

FIG. 17 illustrates a structure in which the memory chip and thecontroller chip are stacked by utilizing an LOC (lead-on-chip).Reference numerals 73 a to 73 g denote some of the leads of a lead framefor the LOC. The leads 73 e and 73 f for the power sources Vcc, Vss areextending like hooks and are forming path bars 74A and 74B. Thenonvolatile memory chip 34 is secured to the path bars 74A, 74B, and thecontroller chip 33 is secured to the nonvolatile memory chip 34. Theexternal terminals 50 of the controller chip 33 are connected to theleads 73 a to 73 g through the bonding wires 4. Further, the externalterminals 51 of the controller chip 33 are connected to the externalterminals 52 of the nonvolatile memory chip 34 by the direct interchipbonding method using the bonding wires 70. In order to decrease theresistance for feeding the operation power sources Vss, Vcc to thenonvolatile memory chip 34, however, the path bars 74A and 74B areconnected to the nonvolatile memory chip 34 through the bonding wires75, 75. The varistors 11 a to 11 e are surface-mounted on thecorresponding leads using an electrically conducting paste such as Agpaste.

FIG. 18 illustrates a still further IC card employing the COB structure.FIG. 19 is a vertical sectional view of the IC card, and FIG. 20 is aview illustrating the electrically conducting pattern formed on thebottom surface of the card substrate of the IC card of FIG. 18.Electrically conducting patterns 80 a to 80 g are formed on the bottomsurface of the card substrate 84, and openings 81 a to 81 g are formedin the card substrate 84 being corresponded thereto. The electricallyconducting patterns 80 a to 80 f constitute connection terminals exposedfrom the IC card. The semiconductor integrated circuit chip 83 isconnected to the electrically conducting pattern 80 f via the opening 81g and is served with ground voltage Vss as a substrate potential.Bonding pads 85 a to 85 f constituting the external terminals of thesemiconductor integrated circuit chip 83 are connected to the connectionelectrodes 80 a to 80 f using the bonding wires 86 through the openings81 a to 81 f. Then, varistors 82 a to 82 e comprising chieflysemiconductor ceramics are surface-mounted across the connectionterminals 80 a to 80 g and the electrically conducting patterns 80 gthrough the openings 81 a to 81 g using an electrically conducting pastesuch as Ag paste in order to reinforce the prevention of electrostaticdamage to the semiconductor integrated circuit chip 83 in the samemanner as described above.

<Notice>

FIG. 21 illustrates an IC card having a notice for preventing theelectrostatic damage. An IC card such as the multi-media card mountingthe semiconductor integrated circuit chip with plural connectionterminals being exposed, is provided on its surface with a notice 90,such as “DON'T TOUCH THE CONNECTION TERMINALS” as shown in FIG. 21(A) sothat the user will not touch the connection terminals 3 a to 3 g. Onthis region may further be written a production management code. Asshown in FIG. 21(B), further, an indication is provided to clearlyindicate the position for holding the IC card by fingers, such as noticeindication 91 in the form of a finger printed on a position where the ICcard should be held by fingers at the time of attachment or detachment.As shown in FIG. 21(B), further, a packing material 92 such as alaminated film, a paper box or a plastic casing packing the IC card maybe provided with a notice 93 warning not to touch the connectionterminals 3 a to 3 g of the IC card.

The notices 90, 93 and indication 91 are helpful for preventing the ICcard from being electrostatically damaged due to unexpected handling bya person who is not familiar with the IC card.

<How to Fabricate the IC Card>

FIG. 22 illustrates a method of fabricating the IC card shown in FIGS. 4and 5. First, varistors are mounted on the predetermined electricallyconducting patterns of the card substrate such as a PCB substrate or atape substrate (S1). In practice, a solder paste or a silver paste isused. Thereafter, the paste is cured (baked) (S2), and a required numberof the semiconductor integrated circuit chips are die-bonded to theelectrically conducting pattern on the card substrate (S3). Then, thesurface of the card substrate is cleaned with a plasma (S4). Then, thebonding pads of the semiconductor integrated circuit chips that aredie-bonded are bonded to the electrically conducting pattern by thermalultrasonic method using gold bonding wires (S5). The semiconductorintegrated circuit chips and the bonding wires are then sealed bypotting the resin (S6) which is then cured by baking (S7). Finally, ametal cap is secured onto the card substrate by adhesion or by plasticinsert molding.

As described above, the varistors are first mounted on the cardsubstrate and, then, the semiconductor integrated circuit chips aredie-bonded or wire-bonded. Therefore, the protection by the varistors isaccomplished at the time of assembling the IC card, contributing toimproving the yield of the IC card. The varistors, however, may bemounted afterwards depending upon the convenience in the production,such as temperature conditions, etc.

<Data Recovery Terminals>

FIG. 23 illustrates an IC card giving attention to recovering the data.The basic constitution is the same as FIG. 5, and the difference is thepossession of plural data recovery terminals. In FIG. 23, the connectionbetween the control latch 33 and the nonvolatile memory chips 34 a, 34 bis simplified in order to emphasize the connection to the data recoveryterminals. In FIG. 23, the circuit elements having the same functions asthose of FIG. 5 are denoted by the same reference numerals, but theirdetailed description is not repeated.

Though not diagramed in FIG. 5, the controller latch 33 has an inputterminal (also simply written as test terminal /TEST) for receiving atest signal /TEST pulled up in the circuit as one of the externalterminals 51. When a low level is input, the test terminal /TESTcontrols the interface terminal to the nonvolatile memory chips 34 a, 34b and, controls, particularly, the output terminal and the input/outputterminal to assume a state of a high output impedance or to assume astate in which the input/output operation cannot be executed.

On the card substrate 1 are formed data recovery terminals 92 that areconnected to all external terminals 51 of the controller chip 33 on theside of the memory interface in a one-to-one manner through wirings 91.There are further provided a ground terminal 96 for recovering the datathat is connected, through a wire 95, to an external terminal for theground power source Vss among the external terminals 50 of thecontroller chip 33 on the side of the cathode interface, and a powersource terminal 94 for recovering the data that is connected, through awire 93, to an external terminal for the power source voltage Vcc amongthe external terminals 50 of the controller chip 33 on the side of thecard interface. In FIG. 23, reference numeral 90 denotes a guard ringadded to the card substrate 1 for preventing the electrostatic damage.The guard ring 90 surrounds the card substrate 1 and is connected to theground power source terminal of the circuit.

The data evaluation terminals 92, 94 and 96 have been formed on the cardsubstrate 1. When the memory control operation cannot be executed forthe controller chip 33 due to the electrostatic damage, therefore,access can be made directly to the nonvolatile memory chips 34 a, 34 bfrom an external unit through the data evaluation terminals 92, 94 and96. Therefore, even when the controller chip 33 is damaged, the datathat are remaining in the nonvolatile memory chips 34 a, 34 b can beeasily recovered.

The controller chip 33 may have a privacy protection function thatexecutes the encryption for the data to be written into the nonvolatilememory and executes the decryption for the data read out from thenonvolatile memory. In this case, the data are recovered by themanufacturer of the IC card or by an authorized person by decrypting thedata read out from the nonvolatile memory chips.

<Method of Recovering the Data>

FIG. 24 illustrates a procedure of a data recovery processing for the ICcard equipped with the data evaluation terminals.

The data are recovered from a multi-media card (MMC) of which thecontroller became defective due to electrostatic damage that could notbe prevented by the input protection circuit or the varistors (S10). Thedata can further be recovered from those multi-media cards (MMC) ofwhich the connection terminals were physically damaged. First, the cap56 is removed from the object MMC (S11), and a probe such as a tester isbrought into contact with the data evaluation terminals 92, 94, 96(S12). Then, the terminal for receiving the test signal /TEST is fixedto the low level, and the memory interface terminal of the controllerchip 33 is controlled to assume a high impedance state (state in whichthe input/output operation cannot be executed) (S13). Thus, thenonvolatile memory chip contained in the MMC is released from thecontrol operation by the controller chip, and becomes accessibledirectly through the data evaluation terminals 92, 94, 96. In thisstate, the data are read out from the nonvolatile memory chip (S14).Here, the controller chip 33 has the privacy protection function thatexecutes the encryption for the data that are written into thenonvolatile memory chip and executes the decryption for the data readout from the nonvolatile memory. Therefore, the data that are read outare decrypted without passing through the controller chip 33. The thusdecrypted data are written into a new MMC in an ordinary manner throughthe connection terminals 3 a to 3 g (S15). Thus, the new MMC having therecovered data is offered to the user (S16). Here, the specifications ofencryption of the controller chip can be confirmed by a production tracecode of the card or by a production code written in the nonvolatilememory.

Thus, even in case the input circuit of the controller chip 33 iselectrostatically damaged, the data that remain safe in the nonvolatilememory chips 34 a, 34 b can be easily recovered.

<Flush Memory Chip>

Here, the flush memory chip will be described. FIG. 26 illustrates aflush memory chip. In FIG. 26, reference numeral 103 denotes a memoryarray which includes a memory mat, a data latch circuit and a senselatch circuit. The memory mat 103 has many electrically erasable andwritable nonvolatile memory cell transistors. As shown in FIG. 27, thememory cell transistor is constituted by a source S and a drain D formedin the semiconductor substrate or in a memory well SUB, a floating gateFG formed in the channel region via a tunnel oxide film, and a controlgate CG overlapped on the floating gate-via an interlayer-insulatingfilm. The control gate CG is connected to a word line 106, the drain Dis connected to a bit line 105, and the source S is connected to asource line that is not shown.

The external input/output terminals I/O0 to I/O7 are also used as anaddress input terminal, a data input terminal, a data output terminaland a command input terminal. An X-address signal input through theexternal input/output terminals I/O0 to I/O7 is fed to an X-addressbuffer 108 through a multiplexer 107. An X-address decoder 109 decodesinternal complementary address signals output from the X-address buffer108 to drive the word line.

A sense latch circuit that is not shown is provided on one end side ofthe bit line 105, and a data latch circuit that is not shown is providedon the other side thereof. The bit line 105 is selected by a Y-gatearray circuit 113 based on a selection signal output from a Y-addressdecoder 111. A Y-address signal input through the external input/outputterminals I/O0 to I/O7 is preset to a Y-address counter 112, and anaddress signal which gradually increases starting from the preset valueis given to the Y-address decoder 111.

When the data is being output, the bit line selected by the Y-gate arraycircuit 113 is rendered conductive to the input terminal of the outputbuffer 15. When the data is being input, the bit line selected by theY-gate array circuit 113 is rendered conductive to the output terminalof the input buffer 117 through a data control circuit 116. Theconnection among the output buffer 115, input buffer 117 and theinput/output terminals I/O0 to I/O7, is controlled by the multiplexer107. A command fed through the input/output terminals I/O0 to I/O7 isgiven to a mode control circuit 118 via the multiplexer 107 and theinput buffer 117. In addition to feeding the data through theinput/output terminals I/O0 to I/O7, the data control circuit 116 feedsdata of a logical value controlled by the mode control circuit 118 tothe memory array 103.

A control signal buffer circuit 119 receives, as access control signals,the chip enable signal /CE, an output enable signal /OE, a write enablesignal /WE, and a signal /SC for instructing the data latch timing, aswell as a reset signal /RES and a command/data enable signal /CDE. Themode control circuit 118 controls a signal interface function to theexternal unit depending on the state of the signals, and furthercontrols the internal operation according to a command code. When acommand or a data is input to the input/output terminal I/O0 to I/O7,the signal /CDE is asserted. When it is a command, a signal /WE isasserted and when it is a data, the signal /WE is negated. When anaddress is input, the signal /CDE is negated and the signal /WE isasserted. Accordingly, the mode control circuit 118 distinguishes thecommand, data and address that are input in a multiplex manner throughthe external input/output terminals I/O0 to I/O7. The mode controlcircuit 118 asserts a ready/busy signal R/B during the erasing orwriting operation, and informs an external unit of the state thereof.

An internal power source circuit 120 forms various operation sources 121for writing, erasing, verifying and reading, and feeds them to theX-address decoder 109 and to the memory cell array 103.

The mode control circuit 118 controls the flush memory as a wholeaccording to the command. The operation of the flush memory is basicallydetermined by the command. The command assigned to the flush memory isread out, erased or written.

The flush memory has a status register 122 for indicating the internalstate, and its content can be read out through the input/output terminalI/O0 to I/O7 by asserting the signal /OE.

In the foregoing were concretely described the invention accomplished bythe present inventors by way of an embodiment. It should, however, benoted that the invention is in no way limited thereto only but can bemodified in a variety of ways without departing the spirit and scope ofthe invention.

For example, the present invention can be applied to the memory cardsother than the multi-media card, such as a compact flush memory and thelike. Further, the structure in which the memory chips are stacked in adeviated manner, the structure in which the through holes are deviatedfrom the connection terminals of the IC card, the structure in which thethrough holes are formed outside the molding region, the structure forstitch-bonding the stacked semiconductor integrated circuit chips andarranging the CS input terminals at the end of the chips, the IC card inwhich the stacked nonvolatile memories are mounted being divided intoplural groups, and the IC card having note and data recovery terminals,are not necessarily limited to those constitutions having varistors. Thememory mounted on the IC card of the present invention is not limited tothe nonvolatile memory but may be a volatile memory (SRAM, DRAM, etc.).Further, the IC card may be the one mounting both the nonvolatile memoryand the volatile memory.

The foregoing description has dealt with the case where the inventionaccomplished by the present inventors was adapted to a memory card in afield of art that served as the background of the invention. The presentinvention, however, is in no way limited thereto only, but can beapplied to IC cards such as a bankbook, a credit card, an ID card, etc.

Briefly described below are the effects obtained by representativeexamples of the invention disclosed in this application.

That is, an IC card is provided that is capable of reinforcing theprevention of the electrostatic damage without increasing the cost ofthe semiconductor integrated circuit chip.

It is allowed to reinforce the prevention of the electrostatic damage byexternally attaching the overvoltage protection elements to thesemiconductor integrated circuit chip without causing a great change inthe size and thickness of the IC card.

It is expected to prevent the electrostatic damage to the IC card due tounexpected handling by a person who is not familiar with.

There is provided an IC card capable of easily recovering the data inthe memory card when the data remain safe in the memory even when theinput circuit of the semiconductor integrated circuit chip iselectrostatically damaged.

It is allowed to avoid the wiring patterns or the bonding wires frombeing densely concentrated, that could become a cause of malfunction dueto undesired leakage of the signal lines even though a vacant region isdecreased on the card substrate of the IC card due to the countermeasureagainst the electrostatic damage by externally attaching circuitelements such as varistors or the like.

It is allowed to realize an IC card having a relatively large storagecapacity despite of its relatively small size.

1. A memory card comprising: a substrate having a front surface and arear surface opposite to said front surface; a first flash memory chiparranged over said front surface of said substrate; a controller chipfor said first flash memory chip arranged over said front surface ofsaid substrate; a first conductive pattern arranged over said frontsurface of substrate; and a plurality of external terminals arrangedover said rear surface of said substrate, wherein said controller chipis stacked over said first flash memory chip, wherein said controllerchip includes a first bonding pad and a second bonding pad, wherein saidfirst flash memory chip includes a third bonding pad, wherein said firstconductive pattern is connected to said first bonding pad by a firstbonding wire, and wherein said second bonding pad is connected to saidthird bonding pad by a second bonding wire.
 2. A memory card accordingto the claim 1, wherein said memory card further comprises a pluralityof test terminals arranged over said substrate and electricallyconnected to said first flash memory chip.
 3. A memory card according tothe claim 2, wherein said memory card further comprises a resin formedover said front surface of said substrate, wherein said resin is moldedover said controller chip, said first flash memory chip and firstconductive pattern, wherein said external terminals and said testterminals are exposed from said resin.
 4. A memory card according toclaim 1, wherein said external terminals include a CLK terminal, a DATterminal and a CMD terminal.
 5. A memory card according to claim 1,wherein the number of said external terminals is
 7. 6. A memory cardaccording to claim 1, wherein a planar area of said first flash memorychip is larger than that of said controller chip.
 7. A memory cardaccording to claim 1, further comprising a second flash memory chip. 8.A memory card according to claim 7, wherein said second flash memorychip is stacked over said first flash memory chip.
 9. A memory cardaccording to claim 1, wherein planar dimension of said memory card areset to 32 mm×24 mm.
 10. A memory card according to claim 1, wherein athickness of said memory card is set to 1.4 mm.
 11. A memory cardcomprising: a substrate having a front surface and a rear surfaceopposite to said front surface; a first flash memory chip arranged oversaid front surface of said substrate; a controller chip for said firstflash memory chip arranged over said front surface of said substrate; aplurality of conductive patterns arranged over said front surface ofsaid substrate; a resin molded over said controller chip, said firstflash memory chip and said conductive patterns; and a plurality ofexternal terminals arranged over said rear surface of said substrate,said external terminals being exposed from said resin and electricallyconnected to said conductive patterns via a plurality of through holes,wherein said controller chip is stacked over said first flash memorychip, wherein said controller chip includes a first bonding pad and asecond bonding pad, wherein said first flash memory chip includes athird bonding pad, wherein one of said conductive patterns is connectedto said first bonding pad by a first bonding wire, and wherein saidsecond bonding pad is connected to said third bonding pad by a secondbonding wire.
 12. A memory card according to the claim 1, wherein saidmemory card further comprises a plurality of test terminals arrangedover said substrate and electrically connected to said first flashmemory chip.
 13. A memory card according to claim 1, wherein saidexternal terminals include a CLK terminal, a DAT terminal and a CMDterminal.
 14. A memory card according to claim 1, wherein the number ofsaid external terminals is
 7. 15. A memory card according to claim 1,wherein a planar area of said first flash memory chip is larger thanthat of said controller chip.
 16. A memory card according to claim 1,further comprising a second flash memory chip.
 17. A memory cardaccording to claim 9, wherein said second flash memory chip is stackedover said first flash memory chip.
 18. A memory card according to claim1, wherein planar dimensions of said memory card are set to 32 mm×24 mm.19. A memory card according to claim 1, wherein a thickness of saidmemory card is set to 1.4 mm.